According to Mr. Skin, Amy Adams has a brief actual nude scene in American Hustle. At the 20-minute mark, she bares her right breast getting into bed with Christian Bale.
"Co-stars Erica McDermott and Elisabeth Rohm also flash some pretty appealing cleavage, but it's Amy Adams who pushes the limits by performing a tassel-clad striptease, baring a generous slice of sideboob, bares her right breast as she is getting onto the bed with Christian Bale just before the 20-minute mark, and pulling up her dress to bare buttcheek 59 minutes in."
http://www.mrskin.com/movie-nudity-report-the-wolf-wall-street-american-hustle---15368
American Hustle premiered in limited release on December 20 and is now currently in wider release.